Throughout history, craftsmen have endeavored to produce appealing illumination effects from gemstones, which has historically been by cutting a gemstone such that light may be captured and redirected to the eye of an observer.
A variety of cuts are used on a gemstone such that a plurality of facets are formed on the gemstone. The facets in the crown capture light, whereas facets in the pavilion of the gemstone reflects light by total internal reflection. It is the capture and redirection of light which gives the appearance of a gemstone being illuminated, with the effects of illumination being those including the parameters of brilliance, fire and scintillation.
Cut precision of gemstones affects the performance of gemstones such as diamonds, and a better defined pattern can provide, for example, sharper on-off scintillation and more primary colors in dispersion. Precision cutting is known to maximise the return of all available light applied to a diamond, which is a result of all of the facets being in precise alignment with each other.
When a diamond is cut with such precision that its facet reflections overlap with each other, this produces uniform, kaleidoscopic patterns when observed typically from the crown or the pavilion of a diamond.
In order to achieve such precision, increased stone wastage is required, in addition to increased working times and costs. Only a small portion of the world's diamonds are cut with such precision so as to provide crisp, uniform patterns.
A predominant example of diamonds cut to such precision termed in the art “Hearts and Arrows” precision cut, which are precision cut variations of the traditional 57 faceted round brilliant cut. Such a cut is termed “Hearts and Arrows” as when viewed upside-down (the “pavilion”) the overlapping reflections create a pattern of eight symmetrical hearts in the pavilion, and when viewed upside-right (the “crown”) eight radiating arrows in the crown may be seen. Devices for viewing such diamonds and light reflection phenomena, light from above is coded white and light from the sides is coded, for example blue, or red or green.
Other diamond cuts which may provide such phenomena is the Princess cut, which typically has 24-48 facets on the pavilion and 17-29 cut on the crown, and variations of pattern result. Such a cut provides overlapping reflections which create a series of white and red V's in the pavilion of the diamond, and primary “X” pattern running through the crown of the diamonds.
The viewing of such light patterns on diamonds is used to determine the quality of the cut, with typically greater precision cutting providing more uniform or consistent facet reflection patterns with respect to other facet reflection patterns.
Viewer devices for viewing patterns in gemstones, such as “Hearts and Arrows” quality diamonds, are cylindrical devices having a magnifying lens at one end, and a locator for a diamond, and illumination is from ambient light. To view the Arrows pattern, the diamond is inserted such that the crown is faced towards the magnifying lens, and to view the Hearts pattern the pavilion of the diamond is faced towards the magnifying lens.